The chemokine family of peptides is defined on the basis of sequence homology and on the presence of variations on a conserved cysteine motif. Schall (1996) Cytokine 3:165-183; and Oppenheim et al. (1991) Annu. Rev. Immunol. 9:617-648. The family can be subdivided on the basis of this motif into two major subfamilies, in which members of each contain four characteristic cysteine residues. This subdivision therefore defines the CC or .beta.-chemokine family in which the first two cysteines are juxtaposed, and the CXC or .alpha.-chemokine family in which there is an intervening amino acid between the first two cysteines. Two other subfamilies have subsequently been described which have variations in the number of amino acids between the first two cysteine residues. Kelner et al. (1994) Science 266:1395-1399; Domer et al. (1997) J. Biol. Chem. 272:8817-8823; and Bazan et al. (1996) Nature 385:640-644.
Chemokines display a range of in vitro and in vivo functions ranging from proinflammatory activities on a range of cell types to proliferative regulatory activities. All of the functions of the chemokine family are believed to be signaled into a responsive cell using members of the G protein-coupled heptahelical receptor family. To date several .alpha.-chemokine and .beta.-chemokine receptors have been described. See, for e.g., Neote et al. (1993) Cell 72:415-425; Ponath et al. (1996) J. Exp. Med. 183:2437-2448; and Power et al. (1995) J. Biol. Chem. 270:19495-19500.